Thermostat or not

popular beleif is that if you run a lower temp thermostat that your engine will run cooler. That is incorrect because the thermostat opens at a lower temperature, thereby not allowing the coolant in the radiator to fully cool.

Example 195 to a 180 may have a few minutes difference in the opening time, the coolant is now in the radiator a few less minutes, causing it not to cool as much before it enters the engine.

If you want your engine to run cooler, the coolant, either needs more time in the radiator or a larger core radiator.

Also older gauges are not as accurate, either because of age or analog, I would not trust an older gauge.
Have you checked it with an IR temp gun? This will help tell the real temperature of your engine, at inlet of thermostat, intake, heads, or exhaust, just about anywhere you check with it.